Scoliosis is a medical condition in which the spine of a person is curved from side to side, and may also be rotated. X-ray assessment is commonly used to determine scoliosis. Other techniques for determining scoliosis include Moire-fringe mapping, raster-based systems, 360° torso profile scanning and stereo-photogrammetric systems.
Measurement of the Cobb angle based on X-ray images is the primary method for scoliosis assessment. Many radiographs of scoliosis patients must be taken during treatment or over a monitoring period which leads to high doses of exposure to radiation. Therefore, this technique is not suitable for children and adolescents.
Also, the interpretation of results from radiographs is highly subjective. It may be difficult to identify oblique projections of a twisting spine and the Cobb angle largely varies depending on the angle of the X-ray beam to the patient. Also, intra-rater and inter-rate variability of 3 to 5° and 6 to 7° respectively have been reported in the calculation of the Cobb angle. Further, rotation of the spine can affect the degree of the Cobb angle, however, the degree of rotation cannot be considered because no rotation information can be obtained by a standard chest X-ray. X-ray examination requires a special room and trained specialists to operate the X-ray equipment. These factors limit the use of X-ray for scoliosis examination.
Traditionally, scoliosis screening has relied on the Adam's forward blend test (FBT). The FBT does not provide a quantitative description of spine deformity. Therefore, different approaches have been developed aimed at achieving more accurate and objective screening results.
A scoliometer is a ruler-like handheld tool. It is an inclinometer to measure trunk asymmetry or axial trunk rotation (ATR) which is also known as rib hump deformity. The scoliometer provides a quantitative measurement to assess the degree of scoliosis. Different studies have found that the measurement from a scoliometer resulted in high intra-rater and inter-rater variations of ATR values and a high false positive rate. In addition, the scoliometer measurement does not correlate well with the Cobb method. Earlier studies have suggested that a scoliometer should not be exclusively used as a diagnostic tool.
Moire-fringe mapping is used to obtain the 3D shape of the back of a patient. Moire-fringes are generated by a grating projected on the target. The images of the fringes are captured by a video system. A contour line system and a sectional shape of the object are then automatically reconstructed and displayed on monitor by computer. Moire fringe mapping can produce very accurate data with a resolution up to 10 microns. Surfaces at a large angle are not measurable when the fringe density becomes too dense. In addition, the patient's position, body-build, and fat folds are other factors causing inaccuracy to the surface topography. Due to the lack of clinical experience on this technique, there is a poor correlation between the observed body and the underlying scoliosis.
Use of a quantec spinal image system is popular in the United Kingdom. The quantec spinal image system is based on Moire topography and raster-stereo photography. This system uses raster stereography to create an image of a fringe pattern and projected onto the patient's back. The system then produces a Q angle, a coronal plane measurement quantifying the coronal asymmetry reflected from the patient's images. However, this system is complex and relies on the surface topography that is a factor of inaccuracy. Photogrammetric method systems are based on laser scanning or photography technique. The laser scanning and video system offers a fast and accurate 3D measurement of scoliotic deformities which can be spatially recorded within a minute. The output of a digital 3D model provides a resolution up to 1 mm. Using this 3D model, spinal deformations information such as the Cobb angle is derived. These systems provide non-invasive and non-contact measurements. However, all of these techniques are based on the surface topography and none of them are portable or movable.
The Ortelius system developed by OrthoScan Technologies is a radiation-free spatial data capturing system to diagnose and monitor spinal deformities. During examination, the examiner palpates the patient's back to locate the spinous process of each vertebra and records the position of spinous process for all vertebrae using a 3D spatial sensor. The data can then be reconstructed into a computer model for calculating the spinal deformation indices. However, the position of transverse process cannot be obtained. The spinal column rotation cannot be considered. Moreover, the patient needs to be repeatedly palpated during the examination and the process may lead to a certain degree of discomfort. Even though the location of transverse processes are recorded by the 3D spatial sensor, it is manually determined by the operator based on body surface palpation, and this is subjective.